Glycerin recovery process



4 dissolved salts or contain only small quantities readily determined. In general, the proportions b Patented Mar. 26, 1940 GLYCERIN RECOVERY PROCESS Nathan M. Mnookin, Kansas City, Mo., assignor to Speas Development 00., a corporation of Missouri No Drawing. Application March 19, 1938, Serial No. 196,959

11 Claims. (Cl. 260-637) I This invention relates to methods of recovering and in particular, alcohol ethers and esters; for polyhydrlc alcohols fromaqueous solutions conexample, isopropyl alcohol, n-propyl alcohol, sectaining the same and more particularly to methondary butyl alcohol? isobutyl alcohol, furfuryl ods of recovering glycerol from such solutions. alcohol, tetrahydrofurfuryl alcohol, the glycol In my prior application Serial No. 192,397, ethers such as ethylene glycol monomethyl ether, 5 filed February 24, 1938, I described and claimed ethylene glycol monoethyl ether, ethylene glycol methods for removing glycerin from concentrated monobutyl ether, diethylene glycol monoethyl glycerin-fermented mash or wort or from conether, diethylene glycol monobutyl ether and the centrated distillers slop as well as from other like, and the esters such as n-propyl lactate, isoaqueous solutions containing glycerin by means propyl lactate, monoand diacetin and the like, 10 of certain novel selective solvents therein deor mixtures thereof.. scribed. The secondary solvent which may be used in In accordance with my present invention I the combination of solvents in'accordance with have found that glycerin may be removed from my present invention also may be, for example,

aqueous glycerinsolutions by means of a comcertain relatively water-immiscible alcohols of a 15 bmation of solvents which is totally or partially higher molecular weight than ethyl alcohol, and immiscible in water. One of the solvents of this certain derivatives of relatively high molecular combination, hereinafter designated the primary weight alcohols, and in particular, alcohol ethers solvent, is a good preferential solvent for glycerin and esters. Of these second solvents I include,

and may be, and generally is, miscible with water. for example, n-butyl alcohol, tertiary amyl al- 20 The other solvent or solvents, hereinafter desig- 001101, et y ty alcohol, octyl alcohol, methyl nated the secondary solvent, is a solvent or mixamyl alcohol, methyl-n-butyl carbinol, isopropyl ture of solvents which is at least partially and is ether, dichlorethyl ether, benzyl alcohol, benzyl preferably totally immiscible in water and at the ether, butyl lactate, n-propyl' lactate, triacetin same time is a selective solvent for the primary and the like or any mixture thereof. 25 solvent for glycerin in the combination. The The combination of the primary solvent or mixsecondary solvent in the solvent combination ture thereof with the secondary solvent or mixused in accordance with my present. invention ture of secondary solvents is Wholly or largely may also be a solvent for glycerin, although this immiscible with water and exercises a preferenis not essential. However, if the secondary soltial afilnity or selective solvent capacity for glyc- 30 vent in the solvent-combination is also a solvent erin in aqueous glycerin soluti nsfor glycerin, the. quantity f glycerin r ved The proportions of the primary and secondary from an aqueous glycerin solution by a single solvents in the com n may Vary s m w extraction is greater than when the secondary a d ay a y be arrived at pe m ysolvent is not a solvent for glycerin. y a preliminary test 011 a Small Portion of the 35 The solvent combinations used in accordance glycerin-cont inin So t o W a Solvent mixwith the present invention are particularly ture used in accordance with my invention the adapted for use in the recovery of glycerin from qu y of each solvent to be used in the aqueous glycerin solutions which are free from ture to obtain successful extractions may be thereof. They are also particularly adapted for of the prima y and Secondary Solvents in the e n the ecovery of glycerin from 9. glycerolcombination are determined by the particular f m t h or n; ordistillers 1 hich solvents used and by the character of the aqueous has not been concentrated or only slightly conglycerincontaining solutions being treated for centrated until the dissolved solids or salts conthe recovery of glycerin. Ihave obtained, for ex- 45 tent is brought not above 5%. They may, of ample, satisfactory glycerin recovery from an course, also be employed with more concentrated aqueous glycerin solution containing no salts by materials or those having a higher concentration using a combination of solvents consisting of one of dissolved solids or salts. partby volume of isopropyl alcohol and two The primary or water miscible glycerin solvent parts by volume of n-buty1 alcohol. I have found 50 which may be used in the combination of solvents that the quantity of isopropyl alcohol in the in accordance with my present invention may combination may be increased up to about five be, for example, certain alcohols of a higher parts by volume of isopropyl' alcohol to about one molecular weight than ethyl alcohol, and certain part by volume of n-butyl alcohol by the addition derivatives of monoand polyhydrlc alcohols, of some soluble salts to the aqueous glycerin- 55 Primary solvent Secondary solvent 2 parts ethylene glycol monolpart n-hutyl alcohol.

butyl ether.

1 part iuriuryl alcohol. 1 part isopropyl ether. 1 part tetrahydrofuriuryl alcohol. 1 part isopropyl ether. 1 part isopropyl alcohol. 2 parts tertiary-ethyl alcohol.

1 part isopropyl alcohol. 1 part ethyl butyl alcohol.

2 parts isopropyl alcohol. 1 part isopropyl ether.

2 parts n'propyl lactate. 1 part isopropyl ether.

2 parts monoacctin. 1 part isopropyl other.

2 parts diacetin. 1 part ethyl hutyl alcohol. 1 part d acetin. 3 parts n-butyl alcohol.

1 part diacetln. 2 parts henzyl alcohol.

2 parts monoacetin.

1 part triacetin.

Incarrying out the processes embodying my present invention, an aqueous glycerin-containing solution or a glycerin-containing residue such as, for example, a glycerol fermented mash or wort is mixed with about an equal volume of one of the solvent mixtures enumerated above. The mixture is agitated or stirred in any suitable vessel either with or without the application of heat, as desired. If heat is used, a pressure-tight vessel must be employed. After thorough agitation the mixture is allowed to stand until a separation of the material into two phases takes place. The extract phase contains the glycerin solvent mixture and. the extracted glycerin with little or in-some cases, substantially no water, depending upon the solvent mixture employed and the aqueous phase contains the treated material from which the glycerin has been extracted. The extract phase containing the extracted glycerin may then be removed in any desirable manner; for example, by decantation or the like. The extraction may; if desired, be repeated a number of times until all or substantially all of the glycerin is removed from the solution being treated. The total extracts may then be combined and the glycerin separated from the solvent or'solvents in any desirable manner as, for example, by distillation or by the addition of an agent which throws out or discharges the glycerin from solution such as, for example, isopropyl ether, dichlorethyl ether and the like.

In the formation of the two phases mentioned above, the glycerin passes from the concentrate or water phase to the immiscible or substantially immiscible solvent mixture or extract phase. It is, of course, obvious that with given relative proportions of solvent mixture to material treated, the proportion of glycerin passing from the water phase depends in a large measure on the degree of selectivity of the particular glycerin solvent mixture used as well as upon the quantity thereof. Thus, with certain mixtures of solvents larger amounts of glycerin may be removed from the aqueous phase than withlike propor tions of other solvent mixtures. The extent of selectivity or preferential afllnity for glycerin in the solvent mixtures used in accordance with my invention depends upon the nature of the solvents used. In general, I have found that if the solvent mixture contains a solvent or solvents having a propyl (CaH-r) radicaL'these solvent mixtures possess the greatest selectivity or afllnity for glycerin. Thus, for example, in extracting glycerin from a glycerol fermented mash and/or distillers slop, the best results have been attained with, for example, a solvent mixture conmethods for removing glycerin in accordance with my invention and it is, of course, to be understood that my invention is not to be con- I strued as limited to the specific details of the methods described.

Example 1 350 parts by weight of blackstrap molasses in 1250 parts by weight of water, to which has been added 150 parts by weight of sodium sulflte,

are fermented to completion with a yeast, forming substantial proportions of glycerin. The fermented mixture is distilled to remove alcohol, acetaldehyde and other volatile constituents. The residue is mixed withabout an equal volume of a solvent mixture formed by mixing 1 part of isopropyl alcohol and 2 parts of n-butyl alcohol and permitted to stand, whereupon a separation of phases takes place. The extract phase containing the glycerin is removed. The residue may be then extracted'about three or four more times with about an equal volume of fresh solvent mixture in each extraction, and the extracts removed. The extracts, which are substantially water-free, are collected in a suitable vessel and the solvent removed therefrom by a simple distillation. About 50 parts by weight of a light, straw-colored glycerin remains in the vessel containing a relatively small per cent of impurities (including water). This is equivalent to a yield of approximately 75 to 85% of'the glycerin present in the material treated.- The resulting glycerin is of suflicient purity for direct use for many technical purposes.

Example 2 100 parts by volume of an aqueous glycerin solution free from salts containing about 5% by weight of glycerin are mixed in a suitable vessel with about an equal volume of a solvent mixture consisting of one-third by volume of isopropyl alcohol and two-thirds by volume of n-butyl alcohol. The separation of the extract and aqueous phases takes place as described in Example 1, and the extract phase is removed in any desirable manner as described above. A single extraction removes about 50% of the glycerin from the solution. With about three or four extractions substantially all of the glycerin may be removed from the aqueous solution.

The processes embodying my invention are practical and economical and secure an unusually high recovery which closely approaches the quantitles of glycerin present in the glycerin-containing residues or other aqueous solutions treated. The glycerine is separated out in the form of an extract of high glycerin content which is low in water and in some cases almost free from water, and is hence unaccompanied by any substantial quantities of water-soluble salts or nonglycerin compounds which may be present in the material treated. Moreover, by carrying out the processes in accordance with-my invention I am able to obtain directly glycerin of high concentration and having a relatively high degree of purity, under suitable conditions sufllciently pure for technical uses without further concentration or treatment.

In the processes described herein, the solvent mixtures used in accordance with my present invention may, if desired, be added in small portions and with agitation after the addition of each portion. Also, if desired, the processes described herein may be carried out continuously as, for example, by counter-current contacting of an aqueous glycerin solution or glycerol-fermented material with the immiscible or partially immiscible solvent mixtures in any or the known counter-current extraction apparatus. The extraction of the glycerin from the aqueous solutions or glycerin-containing residues as described above may be carried out either hot or cold as desired, and at ordinary atmospheric pressures or at pressures either above or below atmospheric.

The processes embodying my invention may also be used to remove other polyhydric alcohols, such as, for example, glycol, diethylene glycol, propylene glycol, etc. from aqueous solutions containing the same. In the instance where it is desired to remove a polyhydric alcohol, such as a glycol, from an aqueous solution containing the same, any of the solvent mixtures enumerated above and like solvent mixtures may be used to efiect the extraction or removal.

I claim:

1. In the process of recovering glycerin from an aqueous glycerin-containing solution, the-step of treating the solution with a substantially water-immiscible combination of solvents to extract glycerin, one of the solvents of said combination being an organic compound selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters which is a solvent for glycerin at room temperature and another, diiierent from said first named solvent, being an organic compound substantially immiscible in water selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters and at the same time a solvent for said first named solvent.

2. In the process of recovering glycerin from a glycerol-fermented mash, the step of treating the mash with a substantially water-immiscible combination of solvents to extract the glycerin, one of the solvents of said combination being an organic compound selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters which is a solvent for glycerin at room temperature and another, different from said first named solvent, being an organic compound substantially immiscible with water, selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters and at the same time a solvent for said first named solvent.

3. In the process of recovering glycerin from a distillers' slop containing glycerin, the step of treating the slop with a substantially water-immiscible combination of solvents to extract the glycerin, one of the solvents of said combination being an organic compound selected from the class consisting of alcohols oi! higher molecular weight than ethyl alcohol, ethers and esters which is a solvent for glycerin at room temperature and another, different from said first named solvent, being an organic compound substantially immiscible in water selected from the class consisting of alcohols of higher molecular wei ht than ethyl alcohol, ethers and esters which is a solvent for said first named solvent.

4. In the process of recovering glycerin from a glycerin-containing fermentation liquid, the

step of treating the liquid with a substantially water-immiscible combination of solvents to extract the glycerin, one of the solvents oi said combination being an organic compound selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters which is a solvent for glycerin at room temperature and another, difierent from said first named solvent, being an organic compound substantially immiscible in water selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters and at the same time a solvent for said first named solvent.

5. In the process of recovering glycerin from a substantially unconcentrated glycerol-fermented blackstrap molasses mash, the step of treating the mash with a substantially water-immiscible combination of solvents to extract the glycerin, one of the solvents or said combination being an organic compound selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters which is a solvent forglycerin, at room temperature and another, difi'erent from said first named solvent, being an organic compound substantially immiscible in water selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters which is a solvent for said first named solvent.

6. In the process of recovering glycerin from an aqueous glycerin-containing solution, the step of treating the solution with a substantially water-immiscible combination of solvents comprising essentially isopropyl alcohol andtn-butyl alcohol to extract the glycerin.

7. In the process of recovering glycerin from an aqueous glycerin-containing solution, the step of treating the solution with a substantially water-immiscible combination of solvents comprising essentially ethylene glycol monobutyl ether and n-butyl alcohol to extract the glycerin.

8. In the process of recovering glycerin from an aqueous glycerin-containing solution, the step of treating the solution with a substantially waterimmiscible combination of solvents comprising essentially isopropyl alcohol and isopropyl ether to extract the glycerin.

9. In the process of recovering glycerin from an aqueous glycerin solution, the step of treating the solution with a substantially water-immiscible combination of solvents consisting of 1 part by volume of isopropyl alcohol and 2 parts by volume of n-butyl alcohol to extract the glycerin.

' 10. In the process of recovering glycerin from a substantially unconcentrated glycerol-fermented blackstrap molasses mash, the step of treating the mash with a substantially water-immiscible combination of solvents consisting of 1 part by volume of isopropylaicohol and 2 parts by volume of n-butyl alcohol to extract the glycerin.

11. In the processof recovering glycerin from a glycerin-containing material of the class consisting of aqueous glycerin solutions, glycerol fermented mash and distillers slop, the step of treating the material with a substantially waterimmiscible combination of solvents to extract glycerin, one of the solvents of said combination being an oxygenated organic compound selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters which is a solvent for glycerin at room temperature and another, difierent from said first named solvent, being an organic oxygenated compound substantially immiscible in water selected from the class consisting of alcohols of higher molecular weight than ethyl alcohol, ethers and esters and at the same time a solvent for said first named solvent.

NATHAN M. MNOOHIN.

CERTIFICATE OF CORRECTION, Patent No. 2,1915665. March 26, 191p.

NATHAN n. nnooxm.

It is hereby dertified that error appears in the printed specification of the. above numbered patent requiring correction as follows: Page 5, first column, line 5b., claimfi, strike out "miscible combination of solvents consisting of 1" and insert insteada distillrs slop containing glycerin,

the step ofand that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1mm day of May, A. D. 191p.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents; 

